Economics and law have contrasting rhetorics, which is one reason perhaps why economics has become influential in law. It is a new way of arguing, and lawyers are on the watch for new ways of arguing.
These "rhetorics" are not always bad. "Rhetoric" here is not merely ornament and trickery, but all persuasion, from arithmetic to moral character. We humans must decide what arguments we find persuasive. The lawyer's appeal to stare decisis or the economist's claim to scientific status are rhetorical acts, good or bad. I want to argue that economics is a sweet science, but the rhetoric of science in economics is mainly bad, not least because it makes lawyers feel like unscientific imbeciles.
Economics, like mathematics, thinks it uses no rhetoric but logic. One takes premises that someone else is willing to grant and then "proves" some theorem in the usual ways, by construction or by contradiction. The ways of proof are individual, gripping the mind of the individual reasoner. At their most social they are only dialectic (Greek: pick out; converse) - which is the classical name for logic, not "dialectic" in the open sense of Hegel. Dialectic does not view itself as social. Plato's dialectic needs only two people, a victim and a Socratic arguer. Society or culture does not matter for the argument; or so it seems. One could reason logically or dialectically on a desert island, with Friday standing there to nod his head in admiration and say from time to time "panu ge, Sokrates." Economists believe they use Robinson Crusoe reasoning.
Donald N. McCloskey,
The Rhetoric of Law and Economics,
Mich. L. Rev.
Available at: https://repository.law.umich.edu/mlr/vol86/iss4/4